The possibility of obtaining clean, safe water for domestic use is
rather remote in village settings throughout the developing world. The
availability of treated water would be exceptional. Domestic water
supplies are therefore expected to be contaminated with microorganisms
in varying degrees. Such situations would have a bearing on the purity
and safety of the water to be used for the preparation of oral
rehydration solutions, and the risk involved in administering
contaminated solutions.

It is logical, therefore, for UNICEF to recommend the use of boiled
water for the preparation of standard ORS solutions, as is indicated
on the labels of UNICEF packets. It is important though to note that
the water should be allowed to cool before use. This is necessary to
avoid decomposition of the sodium bicarbonate by hot water.

According to the criteria proposed by the WHO Diarrhoeal Diseases
Control Programme (document CDDlSER/81.1), a suitable chemical agent
to be added to the standard ORS ingredients at the time of packing to
ensure decontamination of the reconstituted solution would need to be:

effective against the organisms concerned,

non-toxic to man,

effective in the pH of ORS solution,

non-reactive with the ORS ingredients,

non-reactive with ORS packaging material,

acceptable from the point of view of taste, smell, and colour of the
ORS solution,

non-disruptive of the absorption process in oral rehydration,
inexpensive .

As none of the chemical agents currently used for the sterilization of
water (e.g. chlorine and chlorine compounds) do not meet these
criteria, the WHO Diarrhoeal Diseases Control Programme would not
recommend their use. In this connection, it should be noted that as a
strong oxidizing agent chlorine or its disinfectant compounds
(e.g. sodium or calcium hypochlorite) would react with glucose because
of its reducing properties .
The WHO Diarrhoeal Diseases Control Programme arrives at the
conclusion that boiling is an effective method of decontamination of
water to be used for the preparation of ORS solutions, but has the
following disadvantages:

the difficulty of obtaining fuel and its cost,

the time required for boiling and cooling (and consequently the
delay in commencing therapy),

the risk that, after boiling and cooling, the water or ORS
solution prepared with it may become contaminated during measuring,
mixing, handling, or storage,

the risk that the water may be used for preparing the ORS
solution before it has been sufficiently cooled,

the (perhaps minor) risk that the users will mistakenly boil
the ORS solution after preparation.

On the basis of available information, the following recommendations
have been made regarding the preparation of ORS solutions:

ORS solution should be prepared with water made potable by
recognized methods (e.g. boiling, chlorination, etc.) in containers
washed with such water. This is important because enteric bacteria can
grow in ORS solution, and there are as yet insufficient data to show
that there is no risk associated with the use of "usual" drinking
water;

ORS solution, once so prepared, should be protected against
subsequent contamination and kept in a cool dark place;

If potable water cannot be guaranteed, and ORS solution needs to
be administered, the best available water should be used;

ORS solution, no matter what water is chosen, should ideally be
used within 12 hours and never kept for more than 24 hours.